The invention relates to a valve unit for the hydraulic actuation of the locking means of a mechanical quick-changer for attachments of a construction machine as well as to a quick-change system having such a valve unit and having a quick-change adapter
Quick-change systems serve to allow attachment tools of a construction machine to be changed fast and without complications. This requires a fast connection of both mechanical and hydraulic connections between the attachment tool and the construction machine, in particular the boom system of the machine. So-called quick-change adapters which can be assembled at the construction machine side as required and which include the required components for the fast establishing of a connection to the attachment tool are becoming more and more popular. The mechanical securing of the attachment tool at the adapter is achieved via a locking means of the adapter. A hydraulically actuable bolt mechanism is frequently made use of in this respect whose bolt(s) can be actuated by one or more hydraulic cylinders and can thereby automatically be plugged into the associated bolt receivers at the attachment tool.
The quick-change adapter has to be supplied with hydraulic fluid from a quick-change circuit of the construction machine for the actuation of the locking means or of the hydraulic cylinder respectively. An example for the interconnection of a conventional quick-change circuit can be seen from FIG. 1. The quick-change adapter 5 comprises the said locking means in the form of a hydraulic cylinder 6 whose piston rod actuates, via a coupling mechanism, the they are is plugged, i.e. the attachment tool is locked, and when the piston rod is retracted, the locking bolts are pulled and the attachment tool is unlocked.
The quick-change adapter 5 can be releasably installed at the construction machine, preferably at its boom system. The hydraulic supply of the hydraulic cylinder 6 takes place from the superstructure of the construction machine, for which purpose connectors for the locking and unlocking pressure lines are provided at the adapter 5. The locking and unlocking pressure lines are connected in the adapter itself via directional valves 2, 3 to the piston chamber or ring chamber of the cylinder 6 to trigger the locking/unlocking by a directional valve. The hydraulic supply in the superstructure provides a central 4/3-way directional valve 1 by which a pressure supply for the quick-change adapter 5 and also for further consumers such as the gripper control 4 is provided and controlled. The 4/3-way directional valve 1 for executing specific work procedures is consequently designed with a middle blocking position so that the gripper movement can be blocked. Making use of a central directional valve 1 used for a plurality of consumers requires the integration of the control valves 2, 3 in the quick-change adapter 5; the design of the quick-change adapter thus becomes incomparably more complex. However, this actually makes the operation of the quick-change adapter 5 more difficult at third-party devices, i.e. at construction machines of other manufacturers.
In addition to an improved attachment possibility at third-party devices, it is also desirable to increase the safety level of the quick-change system comprising an adapter and a hydraulic supply since such systems can represent a high risk potential for life and limb of people due to their purpose on a malfunction. The safety-specific focus of corresponding controls has previously primarily been on the electronics or on the operation and consequently on the electrical control or on the position monitoring of the corresponding locking/unlocking valve. This has had the result that sufficient measures were admittedly taken against an unintentional unlocking or actuation by the machine operator, but a single failure or a malfunction of any hydraulic components, e.g. of the locking or unlocking valves, for instance, remained out of consideration in previous studies and developments. However, the malfunction of a single valve can already result in the locking and releasing of the attachment tool in operation.